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these assertions of Mr. Pinkus we have not seen a pure atmosphere of heaven as you quietly glide satisfactory answer; certain it is, that on the 3rd on by an invisible power, and entire freedom from of January, 1839, a patent was taken out by the clanking of cumbrous machinery, flying sparks, Messrs. Clegg and Samuda, from which practical hot cinders, and strong sulphuretted hydrogen. results have been obtained. The grand principle Another advantage is, increased speed-ihe averof the improved atmospheric plan, up to this age rate of travelling by the atmospheric power period, was herinetically sealing the valve with a being fifty miles an hour, while the highest composition each time the train passed. 1838, velocity travelling on the fastest line, by steam, experiments had been made on this plan at Chaillot, is thirty miles an hour; and, in a country where through the exertions of Mr. James Bonfit. Next, time is appreciated as property of great value, an extensive experiment was performed on Worm- this must be considered of paramount importance wood Serubbs, on the West London Railway, did it exist alone; but when speed can be secured Mr. Pinkus' apparatus having been removed, his at less expense, and with increased safety and company falling to the ground for want of funds. comfort, no doubt can exist to which system the The portion of the line selected was half a mile most decided preference is to be given. long, with a rise of 1 in 120 for rather more than “ The plans of atmospheric railways, now fairly half the distance, and 1 in 115 for the remainder. before the public, claim our particular attention. On the 11th of June, 1810, this line was opened The first we notice is that of Clegg and Samuda ; for experiments, and these were attended with and we cannot do better than give the descripsufficient success, and so far sanctioned by the tion drawn up by M. Arago. We shall now say approval of eminent engineers, as to justify further a few words on the manner in which they have proceedings. We should observe, that on the 3rd contrived to establish an immediate and unyielding August, 1839, Mr. Pinkus obtained a third patent, connexion between the piston, on which the atin which he describes a valve and composition mosphere acts as a moving power, and the leadprecisely similar to Clegg and Samuda's; on the ing carriage of a train running outside the tube on 21th March, 1841, a fourth, where he proposes a the ordinary rails. This inflexible connexion, of gaso-pneumatic power. About 1841, Mr. Bonfit which we have just spoken, could not be estabset up at Havre, in the factory of M. Nilbus, lished conveniently, except by means of a metal machinery for manufacturing Clegg and Samuda's rod passing from the piston to the carriage. Now, valve. At the close of 1843, Clegg and Samuda's as it is necessary that this connexion should be plan was laid down on the Dalkey line for the maintained during the entire course of the piston, short distance of one mile and a quarter; this is a there must be a longitudinal opening in the upper continuation of the Dublin and Kingstown line. surface of the tube. is along this upper slit And in the subsequent history of atmospheric that the metal arm travels, by means of which railways, we have last—but, as we imagine, not the movement of the piston is communicated to least--the extraordinary but simple invention of the leading carriage of the train, and thence to all Mr. James Pilbrow, which obtained a patent on the others. This rod, or arm, has been very the 18th November, 1814 ; this invention does justly called the connecting or moving arm, or away with the continuous valve altogether, having plate. But, it may be asked, if there is an openmany other advantages which preceding inventions ing in the tube, how is the vacuum to be procannot claim.

duced? We give the reply. The opening is As the two plans which now chiefly engage continued the whole length of a valve, by which the attention of the public are that of Messrs. it is hermetically closed; the vacuum can be thus Clegg and Samuda, and that of Mr. Pilbrow, we successively produced in that part of the tube to purpose, in a subsequent part of this paper, to the left and right of the piston, as in the closed give a minute description of each of these plans, tube, of which we have spoken in the commenceand a comparative estimate of both. At present ment. By a movement, to which we shall preswe invite your attention to the general advantages ently refer, the valve is partially opened near the of the atmospheric system above steam locomotive piston, so as to let the connecting plate pass ; after power. A diminution of expenditure is one of which it immediately falls by its own weight. the most obvious advantages. In the original out- This is the most delicate part of the apparatus. lay there is not a necessity for that extensive lev. If the valve actually closes the opening, a perfect elling as is now required; engines of very great vacuum is produced and maintained, by which power will not be needed; the wear and tear of we obtain a permanent and powerful moving materials will be diminished ; and, by conse-force. On the contrary, should the valve allow quence, the rates of charges for travelling will be the air to enter by any fissure, we cannot produce lessened, and cheap travelling will be secured a sufficient vacuum but by having recourse to a with a certainty of increased safety and comfort. very powerful air-pump-and, moreover, this imThis advantage of safety is one of paramount im- perfect vacuum can only be supported by the portance. The atmospheric system precludes all continual action of the pump. The longitudinal the terrible calamities of bursting boilers and burn- valve, which closes the opening of the tube, is ing trains, with which the public has become pain- formed of a strip of leather of indefinite length, fully familiar. Running off the line is also strengthened above and below by a series of iron avoided, since, in the atmospheric system, the plates of about a foot long, and not leaving a impelling power is at the centre of gravity, and space between them of more than three eighths must, from its action, keep the train on the rails. of an inch. Weight is thus given to the valve A collision of trains, from which such disastrous without destroying its elasticity. The leather is results have arisen, cannot possibly take place on closely and hermetically fastened by one of its the atmospheric principle. Then, not to enter edges to one side of the opening. The other edge into any metaphysical discussion of the question, remains unattached and movable ; and, when how much the very consciousness of safety pro- the valve is closed, it merely rests on the second motes our comfort—it may suffice to say, that the lip of the opening, which has been previously atmospheric system offers a full enjoyment of the covered in its entire length by a composition of

wax or tallow. When the valve opens, that edge moves, the rod works on the wheels on the inside, of the leather fastened to the tube bends, and thus turns them round, and, as they turn the wheels acts as a true hinge. The valve is never raised outside, the boxes turn also. These external to a perpendicular position ; its movement never wheels are then made to act upon the train, by exceeds an angle of forty-five degrees. The mere means of a rod attached to it, similar to that atfalling of the valve by its own weight does not tached to the piston within ; and thus, as the pisgive it sufficient adherence to the edge of the ton moves along inside the tube, the first carriage opening, so as to prevent the entrance of air into of the train moves along also over it outside the the tube ; therefore it scarcely resumes its place tube, through the medium of this double set of before it is heavily pressed by a wheel fixed at wheels and rods. In attempting to give a comthe back of the leading carriage, to which also is parative estimate of these two plans, it is right attached a cylinder filled with burning charcoal, to state that Clegg and Samuda's plan has most for the purpose of melting the composition of of the general advantages which atmospheric tallow and wax by which the valve is held down. railways have over the present locomotive prinThis is a full description of the Clegg and Samuda ciple. The great distinction, however, between atmospheric railway. Did time allow, we might the system of Messrs. Samuda and that of Mr. also notice a similar plan by M. Hallette, of Pilbrow is this—that in the former the connexion Arras.

between the carriage train and the propulsion “We come now to notice the invention by Mr. piston is direct; in the latter it is indirect, a third Pilbrow, C. E., for which a patent has been taken medium being employed. Another important disout. Now this invention does not appear to be, tinction is that the Samuda system has the prolike many of its predecessors, a mere improve- pulsion tube above ground, and has insuperable ment in some mechanical detail, but seems rather difficulties in crossing roads, and in intersecting to be a new creation-a new system altogether. other lines ; the Pilbrow invention, placing the It might be asked, where Clegg and Samuda's tube below the surface, gets rid of all the objecpatent differs from Pinkus', &c., or what have tions in regard to crossing and diverging lines Clegg and Samuda done? but no one will find it from the main trunk. The continuous valve of necessary to investigate far to discover the differ- the Samuda plan, must necessarily occasion much ence here—no one will ask that question as to leakage, while the Pilbrow plan, dispensing with Pilbrow's. By this plan, the necessity for the the valve altogether, no leakage from that cause continuous valve running along the upper part of can possibly arise. The leakage of Samuda's the tube is entirely avoided; the connexion be- plan is equal to 5-horse power per mile, but Piltween the propulsive principle within and the brow's only 24 horse power during the whole carriages without being obtained in a manner time of working every ten miles; the Samuda entirely distinct. The propulsion tube, instead plan requires an exhausting engine at short interof being broken, or stopped at intervals of a few vals of about two miles and a half; the Pilbrow miles, extends unbroken for the whole distance. plan can be worked with only one engine at the At intervals, on the top of the propulsion tube- interval of ten miles. The Samuda plan is remarksay every thirty feet—there are placed boxes and ably complex, and, therefore, may be subject to supports. Within these boxes are cogged wheels frequent interruptions for repairs. As M. Arago or smooth-surfaced wheels, (a combination of the inquires— Can we hope for future success from two, as the model is now before you,) working a system, into which enters, as principal agents, horizontally on an axle or shaft, the upper portion a strip of leather of immense length, a composition of which passes through an aperture in the top of wax and tallow, and a hot iron to dissolve the of the box, and at the outside, or above these wax? Now, the Pilbrow plan is remarkable boxes, the same axles are made to bear rollers or for its simplicity, and the fewness of agents emwheels similar to those inside the box. The pas-ployed. It is much to be lamented that the Pilsages through which the shafts pass are rerdered brow plan has been attacked, and difficulties asair-tight by the shoulders or flat fillet turned upon cribed to it, for which no grounds whatever exist the shafts. [The lecturer referred to diagrams.) difficulties which have no existence whatever Attached to the propulsion piston is a long rod but in the imagination of the objector. Even the or bar, nearly fitting the small square channel or imagined difficulties must be frankly met, such tube, cast upon the propulsion tube ; and, running as the fine ground metallic surfaces of the along with the piston, is conducted by this smaller wheels soon being injured ;' the friction and tube between the lower wheels. Either side of wear of the spindles by dust ;' but the most forthis bar is covered with cogs, or is smooth, or a midable objection was stated against the use of combination of the two, as the case may be, [the cogs—that great speed would certainly break or lecturer referred to diagrams and model,] corre- strip the cogs. Now, the inventor has stated sponding with the surface of the wheels within in his pamphlet, and in this room, (January 8,) the boxes above described. It should be men- that you may dispense with the cogs, and make tioned, also, that these wheels, or rollers, are use of adhesion, or a combination of the two, at made to project in a slight degree within the high velocities, though it is right here to state, smaller tube. [The lecturer pointed out the dis- that an experiment has been made with the cogs tinction between the adhesion and cog plan ; the at the rate of fifty-five miles per hour, and they latter not being indispensable, but, on the con- did not break or strip. It, however, would be trary, arrangements which many prefer.) As perfectly useless to spend time in refuting objecto the model in particular, which meets all the tions which have been either anticipated or already objections raised against other forms or arrange- proved groundless." ments of this invention, the manner of working One very important point which we deem it the apparatus is simply this :-the air being ex- right to notice, is, that it is immaterial whether hausted from the propulsion tube, the piston, with cog-wheels, threaded-grooved-wheels, or plain its rod attached, is moved along inside it by the surface-wheels, be employed. The principle of pressure of the external atmosphere ; and, as it the invention is the entirely new method by which

the impelling power is connected with the car- there is no dispute. The diameter of Jupiter is riages. And this is the chief feature in the inven- well known to be 94,100, while that of the earth tion, together with the great principle which dis- is 7970. The largest of the satellites of Jupiter tinguishes it from every former invention, viz., in its diameter is not equal to that of the earth. the entire absence of any continuous valve. These respective diameters will give proportionate

areas on the spheres of surfaces capable of reflect

ing solar light. The magnitude of these surfaces From the Polytechnic Review.

will give very different appearances of light acLORD ROSSE's telESCOPE.

cording to the mass which they present, and conIn the" Times” of the 16th April there is a letter immense area, which is so much larger than the

sequently, the reflected light of Jupiter from its from Sir James South descriptive of this magnifi- earth, although at a distance of more than five cent instrument, and of some of the observations times that of the earth from the sun, will receive made by it: there is one upon the occultation of a and reflect a far greater amount of light than the star by the dark part of the moon, which produced earth, or its own satellites, which will account for a phenomenon that, Sir James says, is involved in the intensity of the luminous appearance of Juiimpenetrable mystery. The following is the ac

piter. We judge of the intensities of light by count he gives, and the solution which is now of comparison ;' for instance, a board painted white fered will, perhaps, render the matter apparent.

will appear far darker than writing-paper, and "On the 15th of March, when the moon was writing-paper darker than snow newly deposited. seven days and a half old, I never saw her unillu- The intensity of light, therefore, upon a satellite mined disk so beautifully, nor her mountains so will be greatly less than that of Jupiter : but we temptingly measurable. On my first looking into must go a little farther; light is reflected most the telescope, a star of about the seventh magni- intensely precisely at the angle of incidence. tude was some minutes of a degree distant from Now the reflective spaces on a sphere of small the moon's dark limb. Seeing that its occultation dimensions are very greatly less from this circumby the moon was inevitable, as it was the first oc- stance than the space upon one of far greater area. cultation which had been observed with that tele- If, for instance, any one will hang up a white ball scope, I was anxious it should be observed by its and cast a ray of light upon it, he will find, exnoble maker, and very much do I regret that, cepting in the angle of incidence, which depends through kindness towards me, he would not ac

upon the situation of the eye of the observer, that cede to my wish; for the star, instead of disap- the rest of the parts of the ball, as they recede pearing the moment the moon's edge came in con- from that angle, will become darker. Now, these iact with it, apparently glided on the moon's dark being the premises, we ought not to be surprised face as if it had been seen through a transparent at a satellite possessing so very small a comparamoon, or as if the star were between me and the live share of light, in respect to its primary appear

It remained on the moon's disk nearly two ing dark on passing over the most luminous part seconds of time, and then instantly disappeared at of Jupiter, although it may appear light when 10h. 9m. 59.723. sidereal time.

viewed separately from him, or even whilst pass“I have seen this apparent projection of a star on the moon's face several times, but, from the ing over any of the less illuminated parts of the

planet itself. great brilliancy of the star, this was the most

The small quantity of light that these satelbeautiful I ever saw, " The cause of this phenomenon is involved in incidence, is the reason that these satellites are not

lites reflect, and not its intensity on the angle of impenetrable mystery.”

seen by the naked eye upon the earth. Previous to the occultation, there existed a ray

We trust that the foregoing explanation is of light from the star to the eye of the observer. sufficiently evident, at the same time that we reNow, whether the light is transmitted particle by spectfully submit that if astronomers would make partiele, or whether light is transmitted by undu- themselves masters of a little natural philosophy in lation, which the result of observations and the addition to their great attainments as mathematibalance of probability renders the more certain, cians, they would be able to solve not only many the following effect would be the same.

of the appearances of which we are now cogniThe ray of light represents the star in all its zant, and on which there seems to be an extraordiparts the moment the star is obscured by the pas- nary degree of ignorance, but also to account for sage of the moon, the star itself being fixed, the those new and important facts, which we fully deray would not disappear until the time had elapsed pend upon being made known, by the further use which it takes to pass from the moon to the earth, and contemplated improvement, according to Lea distance of 240,000 miles, this taking up two maire's plan, in Lord Rosse's telescope, for the seconds of time or thereabout, the spectrum of the spirited and able construction of which his Jordstar would remain on the eye during that space, ship has laid the scientific world under enduring and then would instantly be lost. The moon it

obligations.

J. A. BORRON. self continuing to advance would give the spectrum the appearance of passing a short distance upon its face, and, as Sir James says, leading us to sup- son to believe that this undertaking, as it is highly

College of Chemistry.-There is every reapose the star was seen through the moon.

It is to be reSir James South afterwards, in relation to the patronized, will be carried out. passage of the satellites of Jupiter over his face, gretted that the schools already existing are not asks the following question :

considered sufficient for the supply of accomplished

chemists. “Will the telescope tell us why the satellites of Jupiter, which generally pass over Jupiter's face RailwAY UNDER THE THAMES.—The plan for as disks nearly of white light, sometimes traverse forming a railway through the tunnel, proposed it as black patches?

by the late Mr. Samuda, has been submitied to In endeavoring to solve the preceding question, the proprietors. The expense will not exceed ten we shall have to state a few facts about which thousand pounds.

moon.

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From the Polytechnic Review. " The advantages I expect to be derived from

this invention are economy in construction, econoARCHIMEDEAN RAILWAY.

my in power for locomotion, and facility for transMr. Farrell, the inventor of this curious sys- mitting frequent trains with perfect safety. tem, exhibited a model at the Dublin Society's " The facility which the Archimedean possesses house during the late cattle show, and delivered a for ascending inclined planes, places it on a par in lecture on it in the gallery, which was densely this respect with the atmospheric system, by crowded, on Wednesday the 23d ult. After which, as I have before shown, a saving in conalluding to the great advantages which have arisen struction to the amount of 40001. per mile may be from the invention of railways, and to the merits effected, taking the estimate of the Irish railway and demerits of the various plans, Mr. Farrell, commissioners as our standard. The relative estipointing to his model, said :

mates will stand thus : locomotive railway, "I have given this invention the title of Archi- 13,0001. per mile ; atmospheric railway, including medean,' from some resemblance that it bears to the tubes for double line, 18,0001. per mile ; Arthe water-engine, invented by the celebrated Ar-chimedean, including the propeller for double line chimedes, which appears to have been a tube 11,0001. per mile ; these amounts are given, it will coiled spirally round a cylinder ; but as a cylinder be remembered, as merely comparative estimates. of eighteen inches diameter would be expensive On the Archimedean system, therefore, the saving and cumbrous, I substituted a comparatively small in the cost of construction, when compared with shaft of iron-tubing of about four inches diameter, the locomotive, is 2,0001. per mile, and compared and the spiral or thread of the screw I support by with the atmospheric, 7,0001. per mile of double wrought-iron arms of sufficient strength, keyed on line. With respect to the cost of locomotion, it the shaft and bolted to the spiral. The screw pro- will be sufficient for our purpose, as I have before peller thus formed is made in separate lengths of stated, that the locomotive and the atmospheric from twelve to fifteen feet, and connected by coup- systems might be considered nearly on a par as to lings at each joint, that allow a sufficient freedom annual expense, to compare the Archimedean with to meet any accidental sinking of the rails, or any the locomotive system. required divergence from a straight line. These “ As the power is conveyed directly from the lengths rest on metal-bearing saddles that are prime mover to the trains by means of the screw, bolted to the cross-sleepers of the railway. This I cannot conceive that there is any power lost, exscrew propeller is laid down in the middle of the cept that which is absorbed in turning the screw track, and caused to revolve upon its axis by steam propeller and keeping it in motion. The weight or water power, and, when revolving, the spiral of a mile and a half propeller is about eighty tons. rail presses against a pair of wheels that are sus- If we allow the power expended in turning this pended from the frame of the leading carriage of amount to ten-horse power, (and by the use of the train, one wheel being at either side of the friction rollers this might be greatly reduced,) as I axis of the screw ; so that while the carriage is propose a twenty-horse engine to each three mile propelled forward by the pressure of the spiral station of single way, and two such engines on a against the periphery of one of the wheels, it is double line, which could work in concert, each prevented from acquiring accelerated motion or engine would, therefore, have a spare power equal running irregularly forward by the other wheel, to the propulsion of more than 30 tons, at the rate which follows and presses against the spiral on the of 20 miles an hour ; and as trains might be transother side of the axis, and thus aids in giving a mitted in rapid succession without danger of colrevolving motion to the screw propeller. These lision, trains of 20 tons might be transmitted at the wheels, which form the only connection between rate of 30 miles an hour without increasing the the trains and the propeller, are perfectly under engine power, and thus meet the demands of the the control of the conductor, who, by turning the most extensive traffic, at a cost considerably under handle of the vertical screw, can raise them up, one fourth of the expense of locomotive power on and thus disengage them from the propeller, and, the present systems." The saving would therefore by continuing the same action, can apply the be on a railway 100 miles long, 200,0001. in the breaks to the bearing wheels, and thus stop the cost of construction, which at five per cent. is train at any point of the line. It is proposed that 10,0001. per annum, and on the cost of locomotive the stationary engines be placed three miles apart, 75,0001., making a total annual saving of more and that each engine shall turn a mile and a half than 80,0001. per annum on a line of 100 miles in screw propeller in each direction from it ; the length, of very extensive traffic.” Mr. Farrell power will be communicated from the engine by concluded by stating that, startling as those calcumeans of a friction-clutch, let into a cylinder cast lations appeared, he was persuaded they would be on the back of the spur-wheel. By this means, borne out by results. should the shaft meet with any accidental obstruction, it will be saved from any strain. Thus far this invention is applicable to any existing rail

ANASTATIC PRINTING. way; the propeller can be laid down and secured to the cross-sleepers of the railway, and the pro- Mr. Faraday commenced his lecture at the Royal pelling wheels and listing apparatus attached to as Institution on Friday evening last, by expressing many of the carriages as would be required for his fears that, not being in any way connected leading carriages. The model, however, em- with the subject, he might not plead so zealously braces another improvement. It may be seen that in its favor as he did when he brought before them the wheels have no flanges, and there is a pair of his own inventions ; but if he did not render the friction wheels at either end of the carriage that subject quite clear, it was to be considered as enrun against the centre guide rail, that rests tirely his own fault, the inventor having placed on, and is firmly secured to the apex of the tri- every information at his disposal. He hoped to be angular bearing saddles which support the pro- able, even during the short time allotted to the peller.

lecture, to show practically the process, as the

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workman, extremely skilful in the science, could working amidst the excitement and bustle attendshow practically the working. The word “anas- ant upon the lecture. I will now call yout attentatic" signified, he was informed by scholars, a tion to the repulsive action of water and oil. You raising up; in other words, a revival of what are aware that when two smooth surfaces wetted might be considered as dead and useless. Having with either oil or water are pressed together, they given this definition of the name, before showing cohere with considerable force ; there is but little its workings, he had most distinctly to repudiate difficulty in sticking them together, though my the slightest intention of in any way recommend strength is hardly sufficient to tear them apart'; ing it or pledging himself for its success. How- this is not, as was formerly supposed, the cohesion ever it might eventually turn out, his opinion could of the surfaces, but the attraction of particles of never be brought against him, for he had given water for water. We are indebted to Dr. Henry, none. He considered this caution necessary, as of America, for the peculiarly instructive papers he found his name constantly brought forward as and experiments he has published, which, though recommending this theory or that theory, or iden- out of place here, I hope, ere the season closes, to tified indeed with things with which he had not have the pleasure of again alluding to. · (Great the slightest acquaintance. That very day, in- applause.) I will pour upon this plate some coldeed, he had received a letter upon his supposed ored water, and drop on it some oil : the water is, advocacy of perpetual motion. His duty was but to you see, driven to the sides ; and this effect is even explain, as clearly and briefly as he could, the in- seen more strongly when I cover first the plate vention now before them. It consisted in a plan with oil, and pour on the water : it slides, as you of printing from a printed page, or an engraving, see, over the plate ; each, as it were, keeps posany number of copies. He would, to show the session in defiance of the other, the first applied principle, take at random a leaf from the book, and holding possession ; and this is probably one cause give it over to the worker, and they would see the why, after so many impressions, the printing keeps process in all its stages. They would observe that distinct, the repulsive action of the water pressing he wetted first the print freely with dilute nitric up the ink in place of allowing it to spread, even acid. (The proportions the lecturer did not state, though it remains for some time soft. The possibut we should judge its strength to be at least one bility of taking impression by pressure has been of acid to four of water.) This was allowed to well known a long time : by rubbing this newsstand for some time—a few, minutes would be paper strongly, with a piece of wood, against this sufficient in the present case; and they would next damp paper, I can obtain a very fair impression, remark the extreme care of the worker to remove though the force I can employ is of course not for the excess of acid. This was effected by pressure a moment to be compared to the even and powerful between sheets of bibulous or blotting paper; this pressure of the printing press. Now metallic sheet was then placed upon a plate of polished plates resist strongly water when very highly polzinc. He would draw attention to the extreme ished, though, as you observe, I may pour water care with which the worker was polishing the on this plate : its surface is not tarnished ; the plate ; the slightest speck would be sufficient to water moves lazily, like a slug, upon its surface. injure the impression. His hearers would now see A little mucilage will at once remove this diffithe system ; the acid would soak through the pa- culty ; the gum enables it to spread smoothly over per, but on those places where the printing was the surface. There is not quite sufficient mucilage the acid could not penetrale. Printers' ink, as here, (this experiment failed,) but on the addition they were aware, was composed of lamp-black and of a little more the effect is at once apparent. But a preparation of linseed oil, and this effectually I will play further tricks with this plate ; I will defended the plate from the acid. “ The wetted direct the man to rub off the impression from the paper and the plate are then submitted to heavy plate—and this can be done easily by turpentinem pressure between two rollers, and the plate is, as and the plate will be to all appearance as before it you see, strongly acted upon by the water; it is was first submitted. Before doing so I will have now washed with gum-water, and this, though an first the plate entirely inked over ; every part is apparently unimportant part of the process, is of now covered. I place my finger on any part, and great practical importance ; it would appear to have you observe it covered with the ink, marking a most decided repulsive action on the ink. The whatever I now touch. The worker will rub it plate can now be submitted to the action of the with his cloth, and take an impression. You will inken roller; the parts protected by the printing observe that the rubber has moved the ink only will alone receive the iuk, and in order to render from those places to which it was not first applied, this more decided, the zinc plate is now washed and the printing is as clear as before. He will with phosphoric acid ; the action of this acid is now move off the ink entirely, and you would beexceedingly obscure; the phosphoric has no ad- lieve that the plate was now destroyed : but no; vantage over the nitric or muriatic, but the differ- the parts, once inked, though every atom of grease ence where the phosphoric is used is exceedingly has been removed, will still receive only the ink, apparent. Phosphoric acid is easily made, by while the other parts will, as before, reject it; leaving phosphorus in water exposed to the action and again, you see, the printing goes on without of the atmosphere; the phophorus absorbs oxygen, hindrance. Eight thousand impressions have been, and forms the phosphoric acid. The worker, you we believe, taken without the slightest difference see, uses considerable force in his operations with between the first and the last in point of deteriorathe gum-water and the phosphoric acid ; his ex- tion: indeed, the order of perfection is generally perience has shown him that the printing ink ad- reversed, the first being the most incomplete. In heres now with some firmness, and you will be the copying by this process the old printing, there able to see the process of the printing. I hand was a great difficulty presented by the dryness of over to the chairman, as your representative, the the ink, which becomes nearly brittle: to remove impression just worked off; you will, after the this the paper was sponged with a solution of lecture, find it perfect. But it would be unfair to potash : this would soften the ink. The potash judge of the practical working by the process now was afterwards removed by soaking the paper in a

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